The accuracy of the ultrasound measured transverse cricoid diameter and the epiphyseal transverse diameter of the distal radius in predicting the pediatric endotracheal tube size.

BACKGROUND: In everyday pediatric anesthesia practice, clinicians frequently exchange an already inserted endotracheal tube because of a leak or resistance causing significant morbidity. We investigated the accuracy of two ultrasound measurements; the transverse cricoid diameter and epiphyseal diameter of the distal radius in the prediction of endotracheal tube size that best fits in children compared to age-based formulas. PATIENTS: One hundred children (1-6 years) who underwent elective surgery with endotracheal tube whether cuffed (n = 50) or uncuffed (n = 50) were enrolled. The primary endpoint was the agreement between the reference tube size for which its outer diameter was selected based on transverse cricoid diameter and the final best-fit-ETT. The Correlation and Bland Altman agreement tests were conducted between best-fit-ETT outer diameter and ultrasound-measured outer diameter, and between best-fit-ETT inner diameter and inner diameter calculated by age-based formulas. RESULTS: The agreement rate between transverse cricoid diameter-based endotracheal tube size and best-fit-ETT size was 88% in cuffed group compared to 90% in uncuffed group. A significant positive correlation was reported between the outer diameter of best-fit-ETT and the outer diameter measured by the two ultrasound methods. A lower degree of positive correlation was reported between the inner diameter of best-fit-ETT, and the inner diameter calculated by age-based formulas. Bland Altman's analysis showed agreement between best-fit-ETT outer diameter and epiphyseal diameter of the distal radius in both groups and with transverse cricoid diameter in the cuffed group, with no agreement with age-based formulas in either group. CONCLUSIONS: Both transverse cricoid diameter and epiphyseal diameter of the distal radius are reliable predictors of the size of best-fit-ETT pediatric endotracheal tube compared to age-based formulas. To save time and effort, we recommend the US measurement of the epiphyseal diameter of distal radius in the preoperative visit and documenting the predicted tube size with the preoperative assessments.

Comparison of nostril sizes of newborn infants with outer diameter of endotracheal tubes.

BACKGROUND: Recommendations for endotracheal tube (ETT) size usually refer to the inner diameter (ID). Outer diameters (OD), however, vary greatly between manufacturers, which in some brands might cause difficulties in passing the ETT through the nostrils if choosing the nasal route for intubation. Even though the nostrils are dilatable by an ETT, it might be difficult to pass an ETT through the posterior naris (narrowest point of the nasal passage), if the OD is bigger than the nostrils. Therefore, nostril size may provide some guidance for the appropriate ETT size preventing unsuccessful intubation attempts. This study therefore compares nostril sizes of newborn infants with ODs of ETTs from several manufacturers. METHODS: This is a subgroup analysis of a prospective observational study, performed in a single tertiary perinatal centre in Germany. The diameter of the nostril of infants born between 34 and 41 weeks´ gestation was measured in 3D images using 3dMDvultus software and compared to the OD of ETT from five different manufacturers. RESULTS: Comparisons of nostril sizes with ODs of different ETTs were made for 99 infants with a mean (SD) birthweight of 3058g (559) [range: 1850-4100g]. Mean (SD) nostril size was 5.3mm (0.6). The OD of the 3.5mm ETT of different manufacturers ranged from 4.8-5.3mm and was thus larger than the nostril size of 20-46% of late preterm or term infants. Some OD of a 3.0mm ETT were even bigger than the OD of a 3.5mm ETT (e.g. the 3.0mm ETT from Rüsch® has an OD of 5.0mm while the 3.5mm ETT from Portex® has an OD of 4.8mm). CONCLUSIONS: Clinicians should be aware of the OD of ETTs to reduce unsuccessful intubation attempts caused by ETT sizes not fitting the nasal cavity. Generated data may help to adapt recommendations in future. TRIAL REGISTRATION: Subgroup analysis of the "Fitting of Commonly Available Face Masks for Late Preterm and Term Infants (CAFF)"-study: NCT03369028, www.ClinicalTrials.gov , December 11, 2017.

Selection of appropriate endotracheal tube size using thoracic radiography in Beagle dogs.

OBJECTIVE: To determine the optimal endotracheal tube size in Beagle dogs using thoracic radiography. STUDY DESIGN: Prospective, randomized, crossover experimental study. ANIMALS: A total of eight healthy adult Beagle dogs. METHODS: Lateral thoracic radiographs were used to measure the internal tracheal diameter at the thoracic inlet. This measurement was multiplied by 60, 70 and 80% to determine the outer diameter of the endotracheal tube for each dog. In each treatment, medetomidine (5 µg kg-1) was administered intravenously (IV) for premedication. Anesthesia was induced with alfaxalone (2 mg kg-1) IV and maintained with isoflurane. After induction of anesthesia, the resistance to passage of the endotracheal tube through the trachea was scored by a single anesthesiologist. Air leak pressures (Pleak) were measured at intracuff pressures (Pcuff) of 20 and 25 mmHg (27 and 34 cmH2O). The results were analyzed using Friedman tests and repeated measures anova. RESULTS: There were statistically significant increases in resistance as the endotracheal tube size increased (p = 0.003). When Pcuff was 20 mmHg, mean Pleak for the 60, 70 and 80% treatments were 9.7 ± 6.7, 16.2 ± 4.2 and 17.4 ± 3.9 cmH2O, respectively, but no significant differences were found. When Pcuff was 25 mmHg, mean Pleak for the 60, 70 and 80% treatments were 10.6 ± 8.5, 19.7 ± 4.9 and 20.8 ± 3.6 cmH2O, respectively, and statistically significant increases were found between treatments 60 and 70% (p = 0.011) and between treatments 60 and 80% (p = 0.020). Three dogs in the 80% treatment had bloody mucus on the endotracheal tube cuff after extubation. CONCLUSIONS AND CLINICAL RELEVANCE: Results based on resistance to insertion of the endotracheal tube and the ability to achieve an air-tight seal suggest that an appropriately sized endotracheal tube for Beagle dogs is 70% of the internal tracheal diameter measured on thoracic radiography.

Predicting endotracheal tube size from length: Evaluation of the Broselow tape in Indian children.

BACKGROUND AND AIMS: Several formulae are available to estimate endotracheal tube (ETT) size in children. This study was designed to compare the ETT estimated by the Broselow tape (BT) with age-based estimation of ETT size and to identify the most accurate formula for the prediction of uncuffed ETT size in Indian children. MATERIAL AND METHODS: Pediatric patients aged 1 month-6.5 years undergoing emergency or elective surgery under general anesthesia requiring endotracheal intubation with uncuffed ETT were included in this study. The ETT size was selected based on the age formula (Penlington formula). The ETT used was deemed to be of correct fit based on the delivery of adequate tidal volume and presence of minimal leak at 20 cm H2O. The actual ETT used was compared with that predicted by age, length of the child, BT, and fifth fingernail width of the child using Pearson's correlation. RESULTS: In children aged <6 months, the ETT used was found to correlate with length (r = 0.286, P = 0.044) and finger nail width (r = 0.542, P < 0.001) of the children. In children >6 months, the ETT used correlated with that predicted from age, BT, length, and fingernail width of the children. In our study, BT has an overall correct predictability rate of 50.3% whereas the age-based formula has a correct prediction rate of 59.8% and length-based formula is 48.7% accurate. CONCLUSION: Length of the child has a good correlation with size of the ETT to be used in Indian children across all age groups. BT is an effective tool to predict ETT size in children >6 months.

Airway Management and Risk Factors for Prolonged Intubation in Patients with Severe Croup.

Croup is a common respiratory illness in children with a substantial variation in the severity of symptoms. Most of the patients present with mild symptoms, but patients with severe croup require intensive care unit (ICU) management. The aim of this study was to investigate the airway management of patients with severe croup who required intubation and determine the risk factors for prolonged intubation. We performed an 18-year retrospective observational cohort study at the pediatric ICU of a tertiary children's hospital in Japan. A total of 16 patients with croup who were intubated for upper airway obstruction were included in the study. Most patients (13of 16, 81%) were intubated with an endotracheal tube (ETT) smaller than their age-appropriate size. The median difference in the internal diameter (ID) between the selected ETT and the age-appropriate size was 1.0 mm (interquartile range: 0.5-1.0). Multivariate analysis performed on factors affecting the cumulative incidence of extubation revealed that the difference in ID between the selected ETT and age-appropriate size (mm) significantly reduced the duration of intubation (hazard ratio: 0.092, p = 0.03). A downsized ETT without a cuff may be recommended for intubation of patients with croup.

The Effects of Endotracheal Tube Size During Bronchoscopy in Simulated Models of Intubated Patients.

OBJECTIVE: The aim is to use a simulation lung model to assess the possibility of performing bronchoscopy through endotracheal tubes (ETT) less than 8.0-mm while appropriately ventilating patients with normal and ARDS lungs in the setting of SARS-CoV-2. METHODS: Five SHERIDAN® ETTs were used to ventilate SimMan® 3G under respiratory compliance levels representing normal and severe ARDS lungs. Baseline measurements of peak pressure, plateau pressure, and auto-positive end expiratory pressure (auto-PEEP) were recorded at four different inspiratory times (Ti). Three different-sized disposable bronchoscopes were inserted, and all measurements were repeated. RESULTS: Normal lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures <30 cm H2 O, and increasing Ti to minimize peak pressure resulted in low auto-PEEP. Regular bronchoscopes in 7.0-mm ETTs had similar results. Large bronchoscopes in 7.5-mm ETTs generated plateau pressures ranging from 28 to 35 cm H2 O with modest auto-PEEP. Severe ARDS lung model: Slim bronchoscopes in 6.0-mm ETTs resulted in plateau pressures of 46 and an auto-PEEP of 5 cm H2 O. Regular bronchoscopes in 7.0-mm ETTs generated similar results. Large bronchoscopes in 8.0-mm ETTs displayed plateau pressures of 44 and an auto-PEEP of 2 cm H2 O. CONCLUSION: To mitigate risk of laryngeal injury, larger ETTs during bronchoscopy should be avoided. Our data show bronchoscopy with any ETT causes auto-PEEP and high plateau pressures, especially in lungs with poor compliance; however, ETT less than 7.5 mm can be used when considering several factors. Our data also suggest similar studies in patients with varying degrees of ARDS would be informative. LEVEL OF EVIDENCE: NA Laryngoscope, 133:147-153, 2023.

Endotracheal Tube Size Is Associated With Mortality in Patients With Status Asthmaticus.

BACKGROUND: There is limited evidence on the clinical importance of the endotracheal tube (ETT) size selection in patients with status asthmaticus who require invasive mechanical ventilation. We set out to explore the clinical outcomes of different ETT internal diameter sizes in subjects mechanically ventilated with status asthmaticus. METHODS: This was a retrospective study of intubated and non-intubated adults admitted for status asthmaticus between 2014-2021. We examined in-hospital mortality across subgroups with different ETT sizes, as well as non-intubated subjects, using logistic and generalized linear mixed-effects models. We adjusted for demographics, Charlson comorbidities, the first Sequential Organ Failure Assessment score, intubating personnel and setting, COVID-19, and the first PaCO2 . Finally, we calculated the post-estimation predictions of mortality. RESULTS: We enrolled subjects from 964 status asthmaticus admissions. The average age was 46.9 (SD 14.5) y; 63.5% of the encounters were women and 80.6% were Black. Approximately 72% of subjects (690) were not intubated. Twenty-eight percent (275) required endotracheal intubation, of which 3.3% (32) had a 7.0 mm or smaller ETT (ETT ≤ 7 group), 16.5% (159) a 7.5 mm ETT (ETT ≤ 7.5 group), and 8.6% (83) an 8.0 mm or larger ETT (ETT ≥ 8 group). The adjusted mortality was 26.7% (95% CI 13.2-40.2) for the ETT ≤ 7 group versus 14.3% ([(95% CI 6.9-21.7%], P = .04) for ETT ≤ 7.5 group and 11.0% ([95% CI 4.4-17.5], P = .02) for ETT ≥ 8 group, respectively. CONCLUSIONS: Intubated subjects with status asthmaticus had higher mortality than non-intubated subjects. Intubated subjects had incrementally higher observed mortality with smaller ETT sizes. Physiologic mechanisms can support this dose-response relationship.

Prediction of endotracheal tube size in pediatric patients: Development and validation of machine learning models.

Objective: We aimed to construct and validate machine learning models for endotracheal tube (ETT) size prediction in pediatric patients. Methods: Data of 990 pediatric patients underwent endotracheal intubation were retrospectively collected between November 2019 and October 2021, and separated into cuffed and uncuffed endotracheal tube subgroups. Six machine learning algorithms, including support vector regression (SVR), logistic regression (LR), random forest (RF), gradient boosting tree (GBR), decision tree (DTR) and extreme gradient boosting tree (XGBR), were selected to construct and validate models using ten-fold cross validation in training set. The optimal models were selected, and the performance were compared with traditional predictive formulas and clinicians. Furthermore, additional data of 71 pediatric patients were collected to perform external validation. Results: The optimal 7 uncuffed and 5 cuffed variables were screened out by feature selecting. The RF models had the best performance with minimizing prediction error for both uncuffed ETT size (MAE = 0.275 mm and RMSE = 0.349 mm) and cuffed ETT size (MAE = 0.243 mm and RMSE = 0.310 mm). The RF models were also superior in predicting power than formulas in both uncuffed and cuffed ETT size prediction. In addition, the RF models performed slightly better than senior clinicians, while they significantly outperformed junior clinicians. Based on SVR models, we proposed 3 novel linear formulas for uncuffed and cuffed ETT size respectively. Conclusion: We have developed machine learning models with excellent performance in predicting optimal ETT size in both cuffed and uncuffed endotracheal intubation in pediatric patients, which provides powerful decision support for clinicians to select proper ETT size. Novel formulas proposed based on machine learning models also have relatively better predictive performance. These models and formulas can serve as important clinical references for clinicians, especially for performers with rare experience or in remote areas.

Prediction of Endotracheal Tube Size in Pediatric Population Using Ultrasonographic Subglottic Diameter and Age-Related Formulas: A Comparative Study.

Background: Choosing the correct Endotracheal tube (ETT) size is important in paediatric patients because an inappropriately large and small sized tube has its own disadvantages and chances of re-intubation with different size tube is high. The currently available modalities do not reflect the actual tracheal diameter for selection of endotracheal tube. Ultrasonography (USG) guided evaluation of transverse diameter at subglottic region may be helpful to estimate the proper size of ETT. We tested the hypothesis that Ultrasound guided subglottic diameter better predicts optimal ETT size than existing methods. Aims: To predict the appropriate size of ETT in pediatric patients to avoid multiple attempts of intubation and airway edema using simple noninvasive USG-guided methods. Settings and Design: Design: Prospective study. Settings: Tertiary care hospital. Materials and Methods: Institutional ethical committee clearance no. BMCRI/PS/138/2020-21 was taken. Laryngoscopy and endotracheal intubation were done in 27 pediatric patients of age 2-15 years using a predetermined-sized ETT, estimated by ultrasonography. ETT size was considered optimal when the cuff leak test was negative. If there was resistance to ETT passage into the trachea, the tube was exchanged with one that was 0.5 mm smaller. If the cuff leak test was positive, then the ETT was exchanged for one with the 0.5-mm larger tube. The comparison was done between the size of ETT calculated by USG-guided subglottic diameter, age, height-related formulas, and clinical methods to look for accuracy of prediction for proper ETT size after cuff leak test. Statistical Analysis: The data collected were entered into Microsoft Excel and analyzed using SPSS version 22. IBM Corp. Released 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp. Appropriate parametric and nonparametric tests were applied wherever necessary. Categorical data: Represented in the form of frequencies and proportions. Continuous data: Represented as mean and standard deviation. Paired sample test: Test to identify the mean difference between two quantitative variables. Kappa statistics: To measure the level of agreement. Results: A total of 27 children of age between 2 and 15 years were selected, out of which 15 were male and 12 were female. The accuracy of predicting appropriate ETT size is greater in ultrasound-guided subglottic diameter when compared to conventional clinical assessment and age- and height-related formula and almost the same accuracy as the clinical method. Conclusion: Ultrasound-guided subglottic diameter is an easy, effective, and noninvasive way of predicting accurate ETT size in the pediatric population.

Current Practices in Endotracheal Tube Size Selection for Adults.

OBJECTIVES/HYPOTHESIS: Intubation with inappropriately sized endotracheal tubes (ETT) can cause long-term tracheal and laryngeal injuries often requiring surgical intervention. Although tracheal size has been demonstrated to vary based on height and sex, it is unclear whether these guidelines are regularly implemented in patients undergoing endotracheal intubation. The objective of this study is to determine the rate of appropriate ETT size selection in patients undergoing intubation and assess provider decision making in ETT size selection. STUDY DESIGN: Retrospective cohort study. METHODS: The study population was all patients who underwent endotracheal intubation over a two-week period at a tertiary academic medical center. Data were collected on patient age, gender, height, BMI, comorbidities, ETT size, duration of intubation, bronchoscopies, and type of practitioner who performed the intubation. A height-based nomogram for ETT size selection was used to determine the recommended ETT size for each patient. RESULTS: One hundred five patients met the inclusion criteria. 22% of patients were intubated with an inappropriately large tube, defined as 1.0 mm larger than the recommended size. Women were more likely to be intubated with an inappropriately large ETT (OR = 13.58, P = .001), as were patients with height less than 160 cm (OR = 141, P = .001). Other factors related to disease severity, anticipation for bronchoscopy, and BMI were not risk factors for the use of inappropriately large ETT. CONCLUSIONS: Although there is compelling evidence that height is a strong predictor of tracheal morphology and appropriate ETT size, height-based guidelines have yet to be universally adopted for ETT size selection. Laryngoscope, 131:1967-1971, 2021.

Prediction of uncuffed tracheal tube sizes in children and infants using age/weight-based formulae: A retrospective cross-sectional study.

INTRODUCTION: The age-based formula is commonly used to predict tracheal tube (TT) sizes although its inaccuracy has been reported to reach as high as 60%. We aim to determine a practical formula using age in months and weight in kilograms to predict uncuffed tracheal tube (TT) size in children and infants. METHODS: A retrospective cross-sectional study was conducted on data obtained from a prospective study on children aged less than 9 years who came for elective surgery and received general anesthesia with oroendotracheal tube intubation at Songklanagarind Hospital between September 2008 and December 2012. The uncuffed TT sizes were based on the age-based formulae and the discretion of the attending anesthesiologist. The age (in months), weight (in kg), and final TT size were measured. Univariate and multivariate linear regression analyses were used to find potential predictors of final uncuffed TT size and therefore the best formula. The correlation coefficient (r) for each model was calculated. The kappa statistic was used to measure the agreement between predicted and actual TT size. RESULTS: A total of 668 patients were recruited. The age/weight formulae for infants aged ≤12 months and children aged >12 months were 3.15 + (age [months] × 0.05) + (weight [kg] × 0.05) with r value of 0.75 (n = 216) and 3.83 + (age [months] × 0.017) + (weight [kg] × 0.017) with r value of 0.85 (n = 452), respectively. The formulae correctly predicted 69.0% and 65.0% of actual TT sizes for infants and children, respectively (both p < 0.001). The formulae for malnourished infants and children whose weights were less than the 3rd percentile for age were 2.70 + (weight [kg] × 0.21) (n = 43) and 3.59 + (age [months] × 0.012) + (weight [kg] × 0.056) (n = 105) with r values of 0.81 and 0.87, respectively. CONCLUSION: The age/weight formula can be used to estimate TT size in infants and children. In failure to thrive children, our formula for malnourished children and infants provided high correlation with final TT sizes.

Selecting an Appropriate Cuffed Endotracheal Tube Using Ultrasound of the Cricoid in a Child with Down Syndrome.

A 7-year-old girl (height, 94 cm; weight, 15.1 kg) with Down syndrome was scheduled for right patellar dislocation repositioning. The ultrasonographically measured internal transverse width of the cricoid before intubation was 7.8 mm. Attempted insertion of a cuffed Mallinckrodt® endotracheal tube (ETT) (internal diameter, 5.0 mm; deflated cuff portion, 8.4 mm diameter) failed. In contrast, the insertion of a cuffed Microcuff® ETT (5.0 mm ID; deflated cuff portion, 7.3 mm diameter) was successful. Thicker folds in the deflated cuff of the Mallinckrodt ETT could have hindered passage through the vocal cord, including the cricoid region. It is becoming standard to use the ultrasonographically measured internal width of the cricoid when choosing cuffed paediatric ETTs, and this approach may be suitable for patients with Down syndrome as well. In these children, approximately 20% of uncuffed ETTs inserted were one or two sizes smaller in diameter than those predicted for the same age. We may choose the ETT size in reference to an ultrasonographically obtained internal transverse width of the cricoid, stated outer diameter (OD) by the producer, and the actual OD depending on the cuff bulk instead of a tube size calculation in patients with growth retardation.

Does body mass index predict tracheal airway size?

OBJECTIVES/HYPOTHESIS: To determine the relationship between body mass index along with other anthropomorphic variables as they relate to tracheal airway dimensions. STUDY DESIGN: Retrospective case series. METHODS: This was a radiographic study of 123 consecutive hospitalized patients undergoing tracheotomy over a 4-year period (2007-2011). We measured airway dimensions in axial computed tomography imaging and made comparisons with height, weight, body mass index, gender, and age. Measurements were taken at the first tracheal ring level including anterior-posterior length, width, and calculated area. We expected higher body mass index not to be a good predictor of larger airway dimensions. RESULTS: The linear regression model showed body mass index was significantly inversely related to tracheal width after controlling for gender and age (P = .0389). For every 1 kg/m(2) increase in body mass index, the tracheal width decreased by 0.05 mm. There was a trend for airway area to diminish with increasing body mass index. CONCLUSIONS: These results are consistent with the hypothesis that obese patients do not have larger airways. Our study indicated a trend toward smaller airways as body mass index increased. Specifically, as body mass index increases, tracheal width appears to decrease. This information should help medical professionals avoid the tendency to use a larger tube to secure the airway of an obese patient. Hopefully, this will result in further research into the field and may prevent future airway injuries in a society where obesity has become epidemic. LEVEL OF EVIDENCE: 4 Laryngoscope, 125:1093-1097, 2015.

Predicting the appropriate uncuffed endotracheal tube size for children: a radiograph-based formula versus two age-based formulas.

STUDY OBJECTIVES: To determine whether a radiograph-based formula using the tracheal diameter from a chest radiograph predicted the appropriate endotracheal tube (ETT) size in children, and to compare these results with those produced using age-based formulas. DESIGN: Retrospective, observational study. SETTING: Medical record review. MEASUREMENTS: Data from 537 pediatric patients, aged 3 to 6 years, who underwent orotracheal intubation with an uncuffed ETT, were randomly divided into two datasets: one was used to derive a formula and the other was for validation. A radiograph-based formula was obtained by linear regression modeling between the tracheal diameter at the seventh cervical vertebra (C7) on chest radiography and the appropriate ETT size from the estimation dataset (n=268). The appropriate size was defined as the ETT size when air leak pressure was 10 to 30 cmH2O. The predictive ability of this equation was evaluated using the validation dataset (n=269). The primary outcome was the success rate of the prediction. MAIN RESULTS: The following radiograph-based formula was obtained: ID = 3 + 0.3 × (tracheal diameter at C7). The success rate of the radiograph-based formula was 57%, which is higher than the 32% (P < 0.001) of the standard age-based formula (ID = 4 + age/4) or 43% (P = 0.002) of Penlington's formula (ID = 4.5 + age/4). An underestimation of the actual tracheal size occurred in 65% of cases using the age-based formulas, but in only 19% with the radiograph-based formula (P < 0.001). CONCLUSIONS: The radiograph-based formula may be useful for predicting the appropriate ETT size in children aged 3 to 6 years.